Substrate table, immersion lithographic apparatus and device manufacturing method

ABSTRACT

A substrate table for an immersion lithographic apparatus is disclosed having a recess, configured to receive a substrate of a given size, and a fluid extraction system, configured to extract fluid from a gap between the edge of the substrate and the edge of the recess, the fluid extraction system configured such that the rate of flow of fluid extracted from a localized section of the gap is greater than the rate of flow of fluid extracted from another section of the gap.

This application is a continuation of co-pending U.S. patent applicationSer. No. 14/739,751, filed on Jun. 15, 2015, which is a continuation ofU.S. patent application Ser. No. 12/721,867, filed on Mar. 11, 2010, nowU.S. Pat. No. 9,059,228, which claims priority and benefit under 35U.S.C. §119(e) to U.S. Provisional Patent Application No. 61/160,151,filed on Mar. 13, 2009, and to U.S. Provisional Patent Application No.61/168,359, filed on Apr. 10, 2009. The content of each of the foregoingapplications is incorporated herein in its entirety by reference.

FIELD

The present invention relates to a substrate table, an immersionlithographic apparatus and a device manufacturing method.

BACKGROUND

A lithographic apparatus is a machine that applies a desired patternonto a substrate, usually onto a target portion of the substrate. Alithographic apparatus can be used, for example, in the manufacture ofintegrated circuits (ICs). In that instance, a patterning device, whichis alternatively referred to as a mask or a reticle, may be used togenerate a circuit pattern to be formed on an individual layer of theIC. This pattern can be transferred onto a target portion (e.g.comprising part of, one, or several dies) on a substrate (e.g. a siliconwafer). Transfer of the pattern is typically via imaging onto a layer ofradiation-sensitive material (resist) provided on the substrate. Ingeneral, a single substrate will contain a network of adjacent targetportions that are successively patterned. Known lithographic apparatusinclude so-called steppers, in which each target portion is irradiatedby exposing an entire pattern onto the target portion at one time, andso-called scanners, in which each target portion is irradiated byscanning the pattern through a radiation beam in a given direction (the“scanning”-direction) while synchronously scanning the substrateparallel or anti-parallel to this direction. It is also possible totransfer the pattern from the patterning device to the substrate byimprinting the pattern onto the substrate.

It has been proposed to immerse the substrate in the lithographicprojection apparatus in a liquid having a relatively high refractiveindex, e.g. water, so as to fill a space between the final element ofthe projection system and the substrate. In an embodiment, the liquid isdistilled water, although another liquid can be used. An embodiment ofthe present invention will be described with reference to liquid.However, another fluid may be suitable, particularly a wetting fluid, anincompressible fluid and/or a fluid with higher refractive index thanair, desirably a higher refractive index than water. Fluids excludinggases are particularly desirable. The point of this is to enable imagingof smaller features since the exposure radiation will have a shorterwavelength in the liquid. (The effect of the liquid may also be regardedas increasing the effective numerical aperture (NA) of the system andalso increasing the depth of focus.) Other immersion liquids have beenproposed, including water with solid particles (e.g. quartz) suspendedtherein, or a liquid with a nano-particle suspension (e.g. particleswith a maximum dimension of up to 10 nm). The suspended particles may ormay not have a similar or the same refractive index as the liquid inwhich they are suspended. Other liquids which may be suitable include ahydrocarbon, such as an aromatic, a fluorohydrocarbon, and/or an aqueoussolution.

Submersing the substrate or substrate and substrate table in a bath ofliquid (see, for example, U.S. Pat. No. 4,509,852) means that there is alarge body of liquid that must be accelerated during a scanningexposure. This requires additional or more powerful motors andturbulence in the liquid may lead to undesirable and unpredictableeffects.

In an immersion apparatus, immersion fluid is handled by a fluidhandling system, device, structure or apparatus. In an embodiment thefluid handling system may supply immersion fluid and therefore be afluid supply system. In an embodiment the fluid handling system may atleast partly confine immersion fluid and thereby be a fluid confinementsystem. In an embodiment the fluid handling system may provide a barrierto immersion fluid and thereby be a barrier member, such as a fluidconfinement structure. In an embodiment the fluid handling system maycreate or use a flow of gas, for example to help in controlling the flowand/or the position of the immersion fluid. The flow of gas may form aseal to confine the immersion fluid so the fluid handling structure maybe referred to as a seal member; such a seal member may be a fluidconfinement structure. In an embodiment, immersion liquid is used as theimmersion fluid. In that case the fluid handling system may be a liquidhandling system. In reference to the aforementioned description,reference in this paragraph to a feature defined with respect to fluidmay be understood to include a feature defined with respect to liquid.

One of the arrangements proposed is for a liquid supply system toprovide liquid on only a localized area of the substrate and in betweenthe final element of the projection system and the substrate using aliquid confinement system (the substrate generally has a larger surfacearea than the final element of the projection system). One way which hasbeen proposed to arrange for this is disclosed in PCT patent applicationpublication no. WO 99/49504. As illustrated in FIGS. 2 and 3, liquid issupplied by at least one inlet onto the substrate, desirably along thedirection of movement of the substrate relative to the final element,and is removed by at least one outlet after having passed under theprojection system. That is, as the substrate is scanned beneath theelement in a −X direction, liquid is supplied at the +X side of theelement and taken up at the −X side. FIG. 2 shows the arrangementschematically in which liquid is supplied via inlet and is taken up onthe other side of the element by outlet which is connected to a lowpressure source. The arrows above the substrate W illustrate thedirection of liquid flow, and the arrow below the substrate Willustrates the direction of movement of the substrate table. In theillustration of FIG. 2 the liquid is supplied along the direction ofmovement of the substrate relative to the final element, though thisdoes not need to be the case. Various orientations and numbers of in-and out-lets positioned around the final element are possible, oneexample is illustrated in FIG. 3 in which four sets of an inlet with anoutlet on either side are provided in a regular pattern around the finalelement. Arrows in liquid supply and liquid recovery devices indicatethe direction of liquid flow.

A further immersion lithography solution with a localized liquid supplysystem is shown in FIG. 4. Liquid is supplied by two groove inlets oneither side of the projection system PS and is removed by a plurality ofdiscrete outlets arranged radially outwardly of the inlets. The inletsand outlets can be arranged in a plate with a hole in its center andthrough which the projection beam is projected. Liquid is supplied byone groove inlet on one side of the projection system PS and removed bya plurality of discrete outlets on the other side of the projectionsystem PS, causing a flow of a thin film of liquid between theprojection system PS and the substrate W. The choice of whichcombination of inlet and outlets to use can depend on the direction ofmovement of the substrate W (the other combination of inlet and outletsbeing inactive). In the cross-sectional view of FIG. 4, arrowsillustrate the direction of liquid flow in inlets and out of outlets.

In European patent application publication no. EP 1420300 and UnitedStates patent application publication no. US 2004-0136494, each herebyincorporated in their entirety by reference, the idea of a twin or dualstage immersion lithography apparatus is disclosed. Such an apparatus isprovided with two tables for supporting a substrate. Levelingmeasurements are carried out with a table at a first position, withoutimmersion liquid, and exposure is carried out with a table at a secondposition, where immersion liquid is present. Alternatively, theapparatus has only one table.

PCT patent application publication WO 2005/064405 discloses an all wetarrangement in which the immersion liquid is unconfined. In such asystem the whole top surface of the substrate is covered in liquid. Thismay be advantageous because then the whole top surface of the substrateis exposed to the substantially same conditions. This has an advantagefor temperature control and processing of the substrate. In WO2005/064405, a liquid supply system provides liquid to the gap betweenthe final element of the projection system and the substrate. Thatliquid is allowed to leak (or flow) over the remainder of the substrate.A barrier at the edge of a substrate table prevents the liquid fromescaping so that it can be removed from the top surface of the substratetable in a controlled way. Although such a system improves temperaturecontrol and processing of the substrate, evaporation of the immersionliquid may still occur. One way of helping to alleviate that problem isdescribed in United States patent application publication no. US2006/0119809. A member is provided which covers the substrate in allpositions and which is arranged to have immersion liquid extendingbetween it and the top surface of the substrate and/or substrate tablewhich holds the substrate.

SUMMARY

One difficulty with immersion technology may be caused by the formationof bubbles within the immersion fluid. In particular, if bubbles floatinto the space in between the substrate and projection system, defectsmay be introduced into the image formed on the substrate.

It is desirable, for example, to reduce or minimize the likelihood orimpact of bubbles forming within an immersion lithographic apparatus orto remove all or a number of bubbles that do form before they cantransfer to a position in which the bubbles may reduce the performanceof the immersion lithographic apparatus.

According to an aspect of the invention, there is provided a substratetable for an immersion lithographic apparatus, comprising: a recess,configured to receive a substrate of a given size, the recess having asupport region to support a lower surface of the substrate and an edgeconfigured to be adjacent the edge of a substrate when it is supportedby the support region; and a fluid extraction system, configured toextract fluid from a gap between the edge of the substrate and the edgeof the recess, wherein the fluid extraction system is configured suchthat, in the absence of liquid, the rate of flow of fluid extracted froma localized section of the gap having a given length is greater than therate of flow of fluid extracted from another section of the gap havingthe same length.

According to an aspect of the invention, there is provided a substratetable for an immersion lithographic apparatus, comprising: a recess,configured to receive a substrate of a given size, the recess having asupport region to support a lower surface of the substrate and an edgeconfigured to be adjacent the edge of a substrate when it is supportedby the support region; and a fluid extraction system, configured toextract fluid from a gap between the edge of the substrate and the edgeof the recess, wherein the fluid extraction system comprises a firstduct opening into the gap, configured to extract fluid from the gapsubstantially all round the substrate, and a second duct, opening intothe gap, configured to extract fluid from a localized section of thegap, wherein the smallest dimension of the cross-section of the firstduct is smaller than the smallest dimension of the cross-section of thesecond duct at the point at which the first and second ducts open intothe gap.

According to an aspect of the invention, there is provided a devicemanufacturing method, comprising projecting a patterned beam ofradiation onto a substrate through a fluid provided in a space adjacentthe substrate, wherein the substrate is supported in a recess on asubstrate table, the method comprising extracting fluid from a gapbetween an edge of the recess and the edge of the substrate such that inthe absence of liquid the rate of flow of fluid extracted from alocalized section of the gap having a given length is greater than therate of flow of fluid extracted from another section of the gap havingthe same length.

According to an aspect of the invention, there is provided a devicemanufacturing method, comprising projecting a patterned beam ofradiation onto a substrate through a fluid provided in a space adjacentthe substrate, wherein the substrate is supported in a recess on asubstrate table, the method comprising extracting fluid from a gapbetween an edge of the recess and the edge of the substrate using afluid extraction system that is configured to extract fluid from thegap, wherein the fluid extraction system comprises a first duct, openinginto the gap, configured to extract fluid from the gap substantially allround the substrate, and a second duct, opening into the gap, configuredto extract fluid from a localized section of the gap, wherein thesmallest dimension of the cross-section of the first duct is smallerthan the smallest dimension of the cross-section of the second duct atthe point at which the first and second ducts open into the gap.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIG. 1 depicts a lithographic apparatus according to an embodiment ofthe invention;

FIGS. 2 and 3 depict a liquid supply system for use in a lithographicprojection apparatus;

FIG. 4 depicts a further liquid supply system for use in a lithographicprojection apparatus;

FIG. 5 depicts a further liquid supply system for use in a lithographicprojection apparatus;

FIG. 6 depicts a substrate on a substrate table;

FIGS. 7 and 8 depict an arrangement of a fluid extraction systemaccording to an embodiment of the invention;

FIG. 9 depicts a variation of a feature of the fluid extraction systemdepicted in FIGS. 7 and 8;

FIG. 10 depicts an optional arrangement of a fluid extraction systemaccording to an embodiment of the invention;

FIGS. 11 and 12 depict a further variation of a fluid extraction systemaccording to an embodiment of the invention;

FIG. 13 depicts a further variation of a fluid extraction systemaccording to an embodiment of the invention;

FIGS. 14 and 15 depict a further arrangement of a fluid extractionsystem according to an embodiment of the invention;

FIG. 16 depict a variation of the fluid extraction system depicted inFIGS. 14 and 15;

FIGS. 17 and 18 depict a variation of the fluid extraction system shownin FIGS. 14 and 15; and

FIGS. 19 and 20 depict a further variation of the fluid extractionsystem shown in FIGS. 14 and 15.

DETAILED DESCRIPTION

FIG. 1 schematically depicts a lithographic apparatus according to oneembodiment of the invention. The apparatus comprises:

-   -   an illumination system (illuminator) IL configured to condition        a radiation beam B (e.g. UV radiation or DUV radiation);    -   a support structure (e.g. a mask table) MT constructed to        support a patterning device (e.g. a mask) MA and connected to a        first positioner PM configured to accurately position the        patterning device MA in accordance with certain parameters;    -   a substrate table (e.g. a wafer table) WT constructed to hold a        substrate (e.g. a resist-coated wafer) W and connected to a        second positioner PW configured to accurately position the        substrate W in accordance with certain parameters; and    -   a projection system (e.g. a refractive projection lens system)        PS configured to project a pattern imparted to the radiation        beam B by patterning device MA onto a target portion C (e.g.        comprising one or more dies) of the substrate W.

The illumination system IL may include various types of opticalcomponents, such as refractive, reflective, magnetic, electromagnetic,electrostatic or other types of optical components, or any combinationthereof, for directing, shaping, or controlling radiation.

The support structure MT holds the patterning device MA. It holds thepatterning device MA in a manner that depends on the orientation of thepatterning device MA, the design of the lithographic apparatus, andother conditions, such as for example whether or not the patterningdevice MA is held in a vacuum environment. The support structure MT canuse mechanical, vacuum, electrostatic or other clamping techniques tohold the patterning device MA. The support structure MT may be a frameor a table, for example, which may be fixed or movable as required. Thesupport structure MT may ensure that the patterning device MA is at adesired position, for example with respect to the projection system PS.Any use of the terms “reticle” or “mask” herein may be consideredsynonymous with the more general term “patterning device.”

The term “patterning device” used herein should be broadly interpretedas referring to any device that can be used to impart a radiation beamwith a pattern in its cross-section such as to create a pattern in atarget portion of the substrate. It should be noted that the patternimparted to the radiation beam may not exactly correspond to the desiredpattern in the target portion of the substrate, for example if thepattern includes phase-shifting features or so called assist features.Generally, the pattern imparted to the radiation beam will correspond toa particular functional layer in a device being created in the targetportion, such as an integrated circuit.

The patterning device MA may be transmissive or reflective. Examples ofpatterning devices include masks, programmable mirror arrays, andprogrammable LCD panels. Masks are well known in lithography, andinclude mask types such as binary, alternating phase-shift, andattenuated phase-shift, as well as various hybrid mask types. An exampleof a programmable mirror array employs a matrix arrangement of smallmirrors, each of which can be individually tilted so as to reflect anincoming radiation beam in different directions. The tilted mirrorsimpart a pattern in a radiation beam which is reflected by the mirrormatrix.

The term “projection system” used herein should be broadly interpretedas encompassing any type of projection system, including refractive,reflective, catadioptric, magnetic, electromagnetic and electrostaticoptical systems, or any combination thereof, as appropriate for theexposure radiation being used, or for other factors such as the use ofan immersion liquid or the use of a vacuum. Any use of the term“projection lens” herein may be considered as synonymous with the moregeneral term “projection system”.

As here depicted, the apparatus is of a transmissive type (e.g.employing a transmissive mask). Alternatively, the apparatus may be of areflective type (e.g. employing a programmable mirror array of a type asreferred to above, or employing a reflective mask).

The lithographic apparatus may be of a type having two (dual stage) ormore substrate tables (and/or two or more patterning device tables). Insuch “multiple stage” machines the additional tables may be used inparallel, or preparatory steps may be carried out on one or more tableswhile one or more other tables are being used for exposure.

Referring to FIG. 1, the illuminator IL receives a radiation beam from aradiation source SO. The source SO and the lithographic apparatus may beseparate entities, for example when the source SO is an excimer laser.In such cases, the source SO is not considered to form part of thelithographic apparatus and the radiation beam is passed from the sourceSO to the illuminator IL with the aid of a beam delivery system BDcomprising, for example, suitable directing mirrors and/or a beamexpander. In other cases the source SO may be an integral part of thelithographic apparatus, for example when the source SO is a mercurylamp. The source SO and the illuminator IL, together with the beamdelivery system BD if required, may be referred to as a radiationsystem.

The illuminator IL may comprise an adjuster AD for adjusting the angularintensity distribution of the radiation beam. Generally, at least theouter and/or inner radial extent (commonly referred to as σ-outer andσ-inner, respectively) of the intensity distribution in a pupil plane ofthe illuminator IL can be adjusted. In addition, the illuminator IL maycomprise various other components, such as an integrator IN and acondenser CO. The illuminator IL may be used to condition the radiationbeam, to have a desired uniformity and intensity distribution in itscross-section. Similar to the source SO, the illuminator IL may or maynot be considered to form part of the lithographic apparatus. Forexample, the illuminator IL may be an integral part of the lithographicapparatus or may be a separate entity from the lithographic apparatus.In the latter case, the lithographic apparatus may be configured toallow the illuminator IL to be mounted thereon. Optionally, theilluminator IL is detachable and may be separately provided (forexample, by the lithographic apparatus manufacturer or anothersupplier).

The radiation beam B is incident on the patterning device (e.g., mask)MA, which is held on the support structure (e.g., mask table) MT, and ispatterned by the patterning device MA. Having traversed the patterningdevice MA, the radiation beam B passes through the projection system PS,which focuses the beam onto a target portion C of the substrate W. Withthe aid of the second positioner PW and position sensor IF (e.g. aninterferometric device, linear encoder or capacitive sensor), thesubstrate table WT can be moved accurately, e.g. so as to positiondifferent target portions C in the path of the radiation beam B.Similarly, the first positioner PM and another position sensor (which isnot explicitly depicted in FIG. 1) can be used to accurately positionthe patterning device MA with respect to the path of the radiation beamB, e.g. after mechanical retrieval from a mask library, or during ascan. In general, movement of the support structure MT may be realizedwith the aid of a long-stroke module (coarse positioning) and ashort-stroke module (fine positioning), which form part of the firstpositioner PM. Similarly, movement of the substrate table WT may berealized using a long-stroke module and a short-stroke module, whichform part of the second positioner PW. In the case of a stepper (asopposed to a scanner) the support structure MT may be connected to ashort-stroke actuator only, or may be fixed. Patterning device MA andsubstrate W may be aligned using patterning device alignment marks M1,M2 and substrate alignment marks P1, P2. Although the substratealignment marks as illustrated occupy dedicated target portions, theymay be located in spaces between target portions C (these are known asscribe-lane alignment marks). Similarly, in situations in which morethan one die is provided on the patterning device MA, the patterningdevice alignment marks may be located between the dies.

The depicted apparatus could be used in at least one of the followingmodes:

1. In step mode, the support structure MT and the substrate table WT arekept essentially stationary, while an entire pattern imparted to theradiation beam B is projected onto a target portion C at one time (i.e.a single static exposure). The substrate table WT is then shifted in theX and/or Y direction so that a different target portion C can beexposed. In step mode, the maximum size of the exposure field limits thesize of the target portion C imaged in a single static exposure.

2. In scan mode, the support structure MT and the substrate table WT arescanned synchronously while a pattern imparted to the radiation beam Bis projected onto a target portion C (i.e. a single dynamic exposure).The velocity and direction of the substrate table WT relative to thesupport structure MT may be determined by the (de-)magnification andimage reversal characteristics of the projection system PS. In scanmode, the maximum size of the exposure field limits the width (in thenon-scanning direction) of the target portion C in a single dynamicexposure, whereas the length of the scanning motion determines theheight (in the scanning direction) of the target portion C.

3. In another mode, the support structure MT is kept essentiallystationary holding a programmable patterning device, and the substratetable WT is moved or scanned while a pattern imparted to the radiationbeam is projected onto a target portion C. In this mode, generally apulsed radiation source is employed and the programmable patterningdevice is updated as required after each movement of the substrate tableWT or in between successive radiation pulses during a scan. This mode ofoperation can be readily applied to maskless lithography that utilizesprogrammable patterning device, such as a programmable mirror array of atype as referred to above.

Combinations and/or variations on the above described modes of use orentirely different modes of use may also be employed.

Arrangements for providing liquid between a final element of theprojection system and the substrate can be classed into at least twogeneral categories. These are the bath type arrangement and the socalled localized immersion system. In the bath type arrangementsubstantially the whole of the substrate and optionally part of thesubstrate table is submersed in a bath of liquid. The so calledlocalized immersion system uses a liquid supply system in which liquidis only provided to a localized area of the substrate. In the lattercategory, the space filled by liquid is smaller in plan than the topsurface of the substrate and the area filled with liquid remainssubstantially stationary relative to the projection system while thesubstrate moves underneath that area. A further arrangement, to which anembodiment of the present invention is directed, is the all wet solutionin which the liquid is unconfined. In this arrangement substantially thewhole top surface of the substrate and all or part of the substratetable is covered in immersion liquid. The depth of the liquid coveringat least the substrate is small. The liquid may be a film, such as athin film, of liquid on the substrate. Any of the liquid supply devicesof FIGS. 2-5 may be used in such a system; however, sealing features arenot present, are not activated, are not as efficient as normal or areotherwise ineffective to seal liquid to only the localized area. Fourdifferent types of localized liquid supply systems are illustrated inFIGS. 2-5. The liquid supply systems disclosed in FIGS. 2-4 weredescribed above.

Another arrangement which has been proposed is to provide the liquidsupply system with a fluid confinement structure. The fluid confinementstructure may extend along at least a part of a boundary of the spacebetween the final element of the projection system and the substratetable. Such an arrangement is illustrated in FIG. 5. In thecross-sectional view of FIG. 5, arrows illustrate the direction of fluidflow in and out of openings in the fluid confinement structure. Thefluid confinement structure is substantially stationary relative to theprojection system in the XY plane though there may be some relativemovement in the Z direction (in the direction of the optical axis). Aseal may be formed between the fluid confinement structure and thesurface of the substrate. In an embodiment, a seal is formed between thefluid confinement structure and the surface of the substrate and may bea contactless seal such as a gas seal. Such a system is disclosed inUnited States patent application publication no. US 2004-0207824.

FIG. 5 schematically depicts a localized liquid supply system or fluidhandling structure or device with a body 12 forming a barrier member orfluid confinement structure, which extends along at least a part of aboundary of the space 11 between the final element of the projectionsystem PS and the substrate table WT or substrate W. (Please note thatreference in the following text to surface of the substrate W alsorefers in addition or in the alternative to a surface of the substratetable WT, unless expressly stated otherwise.) The fluid handlingstructure is substantially stationary relative to the projection systemPS in the XY plane though there may be some relative movement in the Zdirection (in the direction of the optical axis). In an embodiment, aseal is formed between the body 12 and the surface of the substrate Wand may be a contactless seal such as a gas seal or fluid seal.

The fluid handling device at least partly contains liquid in the space11 between a final element of the projection system PS and the substrateW. A contactless seal, such as a gas seal 16, to the substrate W may beformed around the image field of the projection system PS so that liquidis confined within the space 11 between the substrate W surface and thefinal element of the projection system PS. The space 11 is at leastpartly formed by the body 12 positioned below and surrounding the finalelement of the projection system PS. Liquid is brought into the space 11below the projection system PS and within the body 12 by liquid inlet13. The liquid may be removed by liquid outlet 13. The body 12 mayextend a little above the final element of the projection system PS. Theliquid level rises above the final element so that a buffer of liquid isprovided. In an embodiment, the body 12 has an inner periphery that atthe upper end closely conforms to the shape of the projection system PSor the final element thereof and may, e.g., be round. At the bottom, theinner periphery closely conforms to the shape of the image field, e.g.,rectangular, though this need not be the case.

The liquid is contained in the space 11 by the gas seal 16 which, duringuse, is formed between the bottom of the body 12 and the surface of thesubstrate W. The gas seal 16 is formed by gas, e.g. air or synthetic airbut, in an embodiment, N₂ or another inert gas. The gas in the gas seal16 is provided under pressure via inlet 15 to the gap between body 12and substrate W. The gas is extracted via outlet 14. The overpressure onthe gas inlet 15, vacuum level on the outlet 14 and geometry of the gapare arranged so that there is a high-velocity gas flow inwardly thatconfines the liquid. The force of the gas on the liquid between the body12 and the substrate W contains the liquid in a space 11. Theinlets/outlets may be annular grooves which surround the space 11. Theannular grooves may be continuous or discontinuous. The flow of gas iseffective to contain the liquid in the space 11. Such a system isdisclosed in United States patent application publication no. US2004-0207824.

The example of FIG. 5 is a so called localized area arrangement in whichliquid is only provided to a localized area of the top surface of thesubstrate W at any one time. Other arrangements are possible, includingfluid handling systems which make use of a single phase extractor or atwo phase extractor as disclosed, for example, in United States patentapplication publication no US 2006-0038968. In an embodiment, a singleor two phase extractor may comprise an inlet which is covered in aporous material. In an embodiment of a single phase extractor the porousmaterial is used to separate liquid from gas to enable single-liquidphase liquid extraction. A chamber downstream of the porous material ismaintained at a slight under pressure and is filled with liquid. Theunder pressure in the chamber is such that the meniscuses formed in theholes of the porous material prevent ambient gas from being drawn intothe chamber. However, when the porous surface comes into contact withliquid there is no meniscus to restrict flow and the liquid can flowfreely into the chamber. The porous material has a large number of smallholes, e.g. of diameter in the range of 5 to 300 μm, desirably 5 to 50μm. In an embodiment, the porous material is at least slightlyliquidphilic (e.g., hydrophilic), i.e. having a contact angle of lessthan 90° to the immersion liquid, e.g. water.

Another arrangement which is possible is one which works on a gas dragprinciple. The so-called gas drag principle has been described, forexample, in United States patent application publication no. US2008-0212046 and U.S. patent application No. 61/071,621 filed on 8 May2008. In that system the extraction holes are arranged in a shape whichdesirably has a corner. The corner may be aligned with the stepping orscanning directions. This reduces the force on the meniscus between twoopenings in the surface of the fluid handing structure for a given speedin the step or scan direction compared to if the two outlets werealigned perpendicular to the direction of scan. An embodiment of theinvention may be applied to a fluid handling structure used in all wetimmersion apparatus. In the all wet embodiment, fluid is allowed tocover the whole of the top surface of the substrate table, for example,by allowing liquid to leak out of a confinement structure which confinesliquid to between the final element of projection system and thesubstrate. An example of a fluid handling structure for an all wetembodiment can be found in U.S. patent application No. 61/136,380 filedon 2 Sep. 2008.

Many types of fluid handling structure are arranged to allow a flow offluid across the space 11 between the final element of the projectionsystem PS and the substrate W in a certain direction. For example, inthe fluid handling system of FIGS. 2 and 3, this is achieved byproviding a plurality of inlets and outlets surrounding the space andselectively providing or extracting liquid through those inlets oroutlets to create the desired flow. In the case of the FIG. 5embodiment, the liquid outlet 13 may comprise a plurality of openingsfor the flow of liquid therethrough in the body 12 of the fluid handlingdevice which openings surround the space 11. Liquid can then be provided(or extracted) through those openings to provide a flow across the space11 in the desired direction. A first set of openings may be provided forthe provision of liquid to the space 11 and a second set of openings maybe provided for extraction of liquid from the space 11. In theembodiment of FIGS. 2 and 3 (to which an embodiment of the presentinvention may be directed), the inlet and outlets can be considered asbeing a plurality of bodies each of which have a surface, which isprovided with an opening for the flow of liquid therethrough.

FIG. 6 depicts schematically a substrate table WT, according to anembodiment of the invention, to support a substrate W. The substratetable WT includes a recess 20 within which the substrate W fits. Therecess 20 may have a support region to support the lower surface of thesubstrate W and an edge that is adjacent to the edge of the substrate Wwhen the substrate is supported by the support region. The recess 20 mayinclude a substrate holder.

In one arrangement, the recess is configured such that, when thesubstrate W is placed within the recess 20, the top surface of thesubstrate W is co-planar with the top surface of the substrate table WT.The recess 20 may be formed integrally as part of the substrate tableWT. Alternatively, the recess 20 may be formed as an opening through acover plate that forms the top surface of the substrate table WT.

During the operation of the immersion lithographic apparatus, thesubstrate table WT and substrate W move relative to the fluid handlingstructure in order to project the desired pattern of radiation throughthe immersion liquid onto different parts of the substrate W. Duringsuch movement, the edge of the substrate W will periodically traversethe fluid supplied or contained by the fluid handling system in thespace between the projection system and the substrate table WT.

Although the recess 20 within the substrate table WT may be configuredto receive a particular dimension of substrate W, there will be a finitegap between the edge of substrate W and the edge of the recess 20. Forexample, the gap may be of the order of 0.5 mm or less, for example inthe range 0.2 mm to 0.5 mm, for example 0.5 mm, 0.3 mm or 0.2 mm. Thisgap 21 may result in the formation of bubbles in the immersion fluid. Inparticular, as the gap 21 passes under the immersion fluid handlingsystem, gas may be trapped within the gap, resulting in the formation ofbubbles which then rise up from the gap 21 into the immersion fluidbetween the projection system and the substrate W.

It has been proposed to extract fluid from the gap between the edge ofthe substrate W and the edge of the recess 20 to reduce the likelihoodof the formation of bubbles within the gap 21 and, where such bubbles doform, to reduce the likelihood of the bubbles rising up from the gap 21.For example, it has been proposed to provide gap openings, through whichto remove fluid from the gap during operation. The gap openings may belocated near the edge of the recess 20, for example at a radiallyoutward position to the substrate W.

However, although such an extraction system may be effective in somesituations, in other situations it may not be fully effective.

As depicted in FIG. 6, a substrate W may include a positioning feature25, such as a notch, which is used to orient the substrate W for variousprocessing operations. At the point at which the positioning feature 25,such as the notch, is located, the gap 26 between the edge of thesubstrate W and the edge of the recess 20 is significantly larger thanthe gap 21 around the rest of the edge of the substrate W. For example,the gap at the notch may be up to approximately 1.5 mm, for example itmay be 1.2 mm.

Where the gap between the edge of the substrate W and the edge of therecess 20 is increased as a result of such a positioning feature 25 onthe edge of a substrate W, such a system to extract fluid from the gapmay not be able to prevent bubbles forming in the gap 26 between theedge of the positioning feature 25, such as a notch, and the edge of therecess 20.

If a bubble does form within the gap 26 adjacent a positioning feature25 on the edge of the substrate W, it may tend to increase in size suchthat a single larger bubble remains rather than plurality of bubblesforming.

Therefore, an embodiment of the invention provides a fluid extractionsystem to extract fluid from the gap between the edge of the substrate Wand the edge of the recess 20 in which the extraction capacity for alocalized section of the gap is greater than that for other sections ofthe gap, for example is greater than for adjacent sections of the gapbetween the edge of the substrate W and the edge of the recess 20.

In particular, the fluid extraction system may be configured such thatthe resistance to fluid flow from the gap is less in the localizedsection of the gap than in the other sections. Accordingly, under thesame conditions, for example in the absence of liquid, the rate of flowof fluid extracted from the localized section is greater than the rateof low of fluid extracted from other sections of the gap having the samelength as the localized section.

Therefore, a substrate W having a positioning feature 25, such as anotch, may be placed on the substrate table WT of an embodiment of thepresent invention such that the positioning feature 25 is aligned withthe localized section having greater fluid extraction capacity. Byarranging the substrate W in this manner, the greater fluid extractioncapacity in the localized section of the gap between the edge of thesubstrate W and the edge of the recess 20 may help ensure that thelikelihood of bubbles forming in the gap 26 between the edge of thepositioning feature 25 on the edge of the substrate W and the edge ofthe recess 20 is sufficiently reduced and/or to help ensure that anybubbles that do form in this region do not rise up from the gap.

For example, the fluid extraction system may be configured such that atotal of approximately 30 to 50 litres per minute of fluid is extractedfrom around the substrate between the edge of the substrate W and theedge of the recess 20. The additional fluid extraction capacity for thelocalized section aligned with the positioning feature 25 on the edge ofthe substrate W may be approximately 0.5 to 1 litre per minute of thisoverall fluid extraction capacity.

Although the positioning feature 25 on the edge of the substrate W asdepicted in FIG. 6 may be a notch, it should be appreciated that otherpositioning features may be used and an embodiment of the presentinvention may be arranged to reduce the likelihood of bubble formationand/or the likelihood of bubbles being released from the gap in theregion adjacent to such a positioning feature. For example, thesubstrate W may instead have a flat 28.

FIGS. 7 and 8 depict an arrangement of a fluid extraction system thatmay be used. In particular, FIG. 7 depicts a cross-section of a fluidextraction system at the localized section of the gap having increasedextraction capacity. In the arrangement depicted, the recess 20 withinwhich the substrate W is located is formed from an opening through acover plate 30. FIG. 7 depicts a substrate W arranged such that thepositioning feature 25, such as a notch or flat, is adjacent to thelocalized section of increased fluid extraction capacity. Accordingly, arelatively large gap 26 exists between the edge of the substrate W andthe edge of the recess 20 at this point.

The fluid extraction system includes one or more first ducts 32 thatopen into the gap between the edge of the substrate W and the edge ofthe recess 20 at an opening 31 that opens directly into the gap 26.Accordingly, fluid may be extracted from the gap between the edge of thesubstrate W and the edge of the recess 20 without passing under thesubstrate W.

In a convenient arrangement, such as that depicted in FIG. 7, theopening 31 may be provided within the edge of the recess 20 such thatextracted fluid is drawn away from the edge of the substrate W. In onearrangement, the opening 31 may be in the form of a slit-like opening inthe edge of the recess 20 that surrounds the recess 20 and is connectedfor fluid flow to a first duct 32 that may include a ring-shapedchannel. The first duct 32 may be connected by a series of passages 33to an under-pressure source or a further channel 34 connected to anunder-pressure source.

In one arrangement, the opening 31 in the edge of the recess 20 andsurrounding the edge of the recess 20 may have a width of approximately50 pm across. As shown, adjacent to the opening 31 in the edge of therecess 20, the edge of the recess 20 may include an inclined surface 20a. This may assist in preventing bubbles from rising from the gapbetween the edge of the substrate W and the edge of the recess 20.

Fluid is drawn from the gap between the edge of the substrate W and therecess 20 through the opening 31 and towards the under-pressure source.The extracted fluid may be gas when the gap is not passing under thefluid handling system, immersion fluid when the gap is passing under thefluid handling system, or a combination of both, for example immersionfluid having one or more bubbles entrained within the immersion fluid.

At the localized section of the gap between the edge of the substrate Wand the edge of the recess 20, namely at the gap 26 between thepositioning feature 25 of the substrate W when it is appropriatelypositioned and the edge of the recess 20, the extraction system includesa further opening 40, connected to a second duct 42 in order to providethe additional extraction capacity at this point in line with anembodiment of the present invention.

As shown in FIG. 7, the second duct 42 may be connected to the sameunder-pressure source or channel 34 as the first duct 32. Furthermore, acontrol valve 43 may be provided in the second duct 42 in order tocontrol the fluid flow through the second duct 42.

For example, the control valve 43 may be closed when no positioningfeature on the edge of a substrate W is located adjacent to the opening40 of the second duct 42 into the gap between the edge of the substrateW and the edge of the recess 20. In such an arrangement, a bleed line 44may be provided that bypasses the control valve 43. Such a bleed linemay provide a constant small flow of fluid through the second duct 42even when the control valve 43 is closed in order to ensure that, forexample, no liquid remains trapped upstream of the control valve 43within the second duct 42.

Alternatively or additionally, the control valve 43 may be used in orderto adjust the increase of fluid extraction capability at the gap 26between the edge of the substrate W at the positioning feature 25 andthe edge of the recess 20 in comparison with the gap 21 between the edgeof the substrate W not including a positioning feature and the edge ofthe recess 20.

It will be appreciated that it may be undesirable for fluid to passunder the substrate W. In particular, it may be desirable to preventimmersion fluid from passing under the substrate W. Accordingly, asexplained above, the fluid extraction system may be configured such thatfluid is extracted from the gap between the edge of the substrate W andthe edge of the recess such that the fluid being extracted does not passunder the substrate W. Furthermore, at the edge of the support region 24to support the substrate W, a seal 50 may be provided to prevent orreduce the flow of fluid from the gap between the edge of the substrateW and the edge of the recess 20 from passing along the under surface ofthe substrate W. As part of the seal 50, or in addition to it, one ormore openings 51 may be provided for extraction of fluid. The one ormore openings 51 may be present at or near the periphery of the recess20. The one or more openings 51 may be arranged such that they arecovered by the substrate W during operation such that fluid may beremoved from under the substrate during operation. Therefore, any fluidthat does pass under the substrate may be extracted.

FIG. 8 depicts in plan view the arrangement depicted in FIG. 7. As willbe apparent from FIGS. 7 and 8, the opening 40 of the second duct 42into the gap 26 between the positioning feature 25 on the edge of thesubstrate W and the edge of the recess 20 may be substantially the samesize as the gap between the edge of the substrate W at the positioningfeature 25 and the edge of the recess 20.

Such an arrangement may help ensure that any bubbles forming in the gap26 between the edge of the substrate W at the positioning feature 25 andthe edge of the recess 20 may be extracted through the second duct 42.Accordingly, the opening 40 of the second duct 42 into the gap 26between the edge of the substrate W at the positioning feature 25 andthe edge of the recess 20 may be up to, for example, 1.5 mm. In onearrangement, the opening may be approximately 1.2 mm across.

It may therefore be appreciated that the increased extraction capacityat the localized section of the gap 21 between the edge of the substrateW and the edge of the recess 20, at which the positioning feature 25 ofthe substrate W may be arranged, may be provided by the use of a secondduct 42 having an opening 40 that is larger than the opening 31connected to a first duct 32 that is used for fluid extraction from theremainder of the gap 21 between the edge of the substrate W and the edgeof the recess 20. In particular, it will be appreciated that thesmallest dimension of the cross-section of the opening 40 of the secondduct 42 into the gap 26 between the edge of the substrate W and the edgeof the recess 20 is larger than the smallest dimension of thecross-section of the opening 31 of the first duct 32 into the gap 21between the edge of the substrate W and the edge of the recess 20.

As shown in FIGS. 7 and 8, the second duct 42 may be configured suchthat the cross-section of the second duct 42 decreases from the point atwhich it opens into the gap between the edge of the substrate W and theedge of the recess 20 to a point 41 downstream of the opening 40. Thisdecrease in cross-sectional area may be provided to help ensure that theopening 40 into the gap between the edge of the substrate W and the edgeof the recess 20 is sufficiently large to ensure that fluid is extractedfrom across the gap 26 between the edge of the substrate W at apositioning feature 25 and the edge of the recess 20, without anexcessive drop in pressure along the second duct 42. This may besignificant where, as depicted in FIG. 7, the second duct 42 isconnected to the same under-pressure source or channel 34 as the firstduct 32. If the second duct 42 were too large in cross-section along itslength, the extraction of fluid through the first duct 32 from aroundthe entirety of the gap 21 between the edge of the substrate W and theedge of the recess 20 may be significantly reduced. In turn, this mayresult in bubbles being released from the gap 21 between the edge of thesubstrate W and the edge of the recess 20 at locations away from thepositioning feature 25.

As shown in FIGS. 7 and 8, the second duct 42 between the opening 40into the gap 26 between the edge of the substrate W and the edge of therecess 20 at the positioning feature 25 and the second point 41 may befrustro-conical in shape, namely may have straight edges 45 incross-section. However, it should be appreciated that otherconfigurations of the second duct 42 may be used. For example, thesecond duct 42 between the opening 40 into the gap between the edge ofthe substrate W and the edge of the recess 20 and the second point 41may be trumpet-shaped, namely may have curved edges 46 in cross-section,such as depicted in FIG. 9.

As explained above, the fluid extraction system of an embodiment of theinvention may provide for increased fluid extraction from the gapbetween the edge of the substrate W and the edge of recess 20.Accordingly, when a substrate W is loaded to the substrate table WT, itmay be oriented such that a positioning feature 25, such as a notch or aflat, is aligned with the localized section having increased fluidextraction capacity in order to reduce or minimize the likelihood ofbubbles forming in the gap between the edge of the substrate W and theedge of the recess 20 in the region of the positioning feature 25.

It should be appreciated that in arrangements of the fluid extractionsystem described herein, one may provide additional localized sectionshaving increased fluid extraction capacity, such that the substrate maybe oriented in more than one position. For example, two localizedsections having increased fluid extraction capacity may be provided suchthat the substrate W may be oriented in the recess 20 on the substratetable WT such that the positioning feature 25 on the edge of thesubstrate W may be aligned with either of the two localized sections ofincreased fluid extraction capacity.

It will be appreciated that by increasing the number of localizedsections having increased fluid extraction capacity, one may increasethe number of possible orientations of the substrate W on the substratetable WT at which the positioning feature 25 on the edge of thesubstrate W may be aligned with a localized section having increasedfluid extraction capacity.

FIG. 10 depicts in plan view a particular arrangement of part of asubstrate table WT having a fluid extraction system with two localizedsections of increased fluid extraction capacity. In particular, in thearrangement depicted in FIG. 10, two second ducts, such as thosedepicted in FIGS. 7 and 8, are provided and configured to open into thegap between the edge of the substrate W and the edge of the recess 20 atrespective openings 55, 56. For clarity, the substrate W is shown inbroken lines. As will be apparent, the substrate W may be oriented inone of two ways, while aligning the positioning feature 25 of thesubstrate W with one of the openings 55, 56. In an embodiment, only oneof the openings 55, 56 provides the increased fluid extraction, i.e.,one opening 55,56 provides increased fluid extraction while the otheropening 55,56 does not.

In a further exemplary arrangement, four such openings, corresponding tosections of the fluid extraction system having increased fluidextraction capacity, may be provided and may be evenly spaced around theperiphery of the recess 20 to receive the substrate W.

As explained above, each of the ducts associated with the additionalopenings used to provide additional fluid extraction capacity mayinclude a control valve. Accordingly, the control valves associated withopenings that are not aligned with a positioning feature 25 on the edgeof a substrate W supported on the substrate table WT may be closed inorder to prevent unnecessary additional fluid extraction.

It should further be appreciated that alternative arrangements ofopenings of the second duct 42 into the gap 26 between the edge of thesubstrate W and the edge of the recess 20 at a positioning feature 25than those described above may be used. In particular, although theopening 40 into the gap 26 may be configured to be the same size as apositioning feature 25 expected to be provided on the edge of asubstrate W, alternative arrangements may be provided. In particular,the opening 40 may be larger than the positioning feature 25 such that,for example, if there are minor variations in the placement of thesubstrate W on the substrate table WT or the size of the positioningfeature 25, substantially all of the positioning feature 25 remainsaligned with part of the opening 40.

Alternatively or additionally, although the opening 40 depicted in FIGS.7 and 8 is substantially circular, it will be appreciated that this maynot be the case. For example, other opening shapes, such as a slot maybe provided. Likewise, a plurality of smaller openings may be providedadjacent to each other that together may be aligned with a positioningfeature of a substrate W.

Furthermore, in other arrangements, a single opening may be connected toa plurality of second ducts used to provide increased fluid extractioncapability within a localized section of the gap between the edge of thesubstrate W and the edge of the recess 20. An example of such anarrangement is depicted in FIGS. 11 and 12. In particular, as depicted,such an arrangement may be used, for example, if the positioning featureexpected to be provided on the edge of a substrate W is a flat 28. Insuch an arrangement, as shown in FIG. 11 in plan view and as shown inFIG. 12 from the side looking from the substrate W towards the recess20, an opening 61 may be provided that corresponds to the section of thegap 62 between the edge of the substrate W and the edge of the recess 20at which the flat 28 is located. A plurality of second ducts 63 may beprovided to connect the opening 61 to an under-pressure source, forexample in a manner corresponding to that described above in relation toFIGS. 7 and 8.

It should further be appreciated that a fluid extraction systemaccording to an embodiment of the present invention may include morethan one arrangement to provide increased fluid extraction capacity in alocalized area. For example, an arrangement such as that depicted inFIGS. 7 and 8 (or variants thereof) may be provided on one side of asubstrate table WT and an arrangement such as that depicted in FIGS. 11and 12 (or variants thereof) may be provided on the other side of thesubstrate table WT, permitting the use of substrates having differentpositioning features to be used with the one substrate table byappropriate orientation of the substrate W such that the positioningfeature is aligned with the appropriate section of the fluid extractionsystem providing increased fluid extraction capacity.

As explained above, the fluid extraction system of an embodiment of theinvention may be configured such that the outlets 31, 40 connected tothe first and second ducts 32, 42, providing fluid extraction from allround the gap between the edge of the substrate W and the edge of therecess 20 and in a localized section, respectively, may be connected toa common under-pressure source or common channel 34 leading to anunder-pressure source.

In an alternative arrangement, the second duct 42, opening into the gap26 between the edge of the substrate W and the edge of the recess 20 atthe positioning feature 25, is connected to a separate under-pressuresource or channel 70 leading to a separate under-pressure source, asdepicted in FIG. 13.

If a plurality of second ducts 42 are provided as discussed above, someor all of these second ducts 42 may share a common under-pressure sourceor may be connected to a common channel 70 leading to an under-pressuresource. However, it should be appreciated that any or all of the secondducts 42 may have a dedicated under-pressure source.

It should further be appreciated that, in an arrangement having aplurality of second ducts 42, some may be connected to the sameunder-pressure source or channel connected to an under-pressure sourceas the first ducts 32, while others are connected to one or moreseparate under-pressure sources. In any such arrangement, it will beappreciated that one or more of the second ducts 42 may include acontrol valve 43 and may further include a bleed line 44 in a mannercorresponding to that discussed above.

FIGS. 14 to 20 depict further arrangements of the fluid extractionsystem according an embodiment of the invention. In these arrangements,the fluid extraction system is configured to provide a localized sectionof the gap between the edge of the substrate W and the edge of therecess 20 with higher fluid extraction capacity than along the remainderof the gap between the edge of the substrate W and the edge of therecess 20 by the provision of an enlarged opening rather than by theprovision of an additional opening as in the arrangements depicted inFIGS. 7 to 13 as discussed above.

In particular, FIGS. 14 and 15 depict an arrangement in which a duct 32opens into the gap between the edge of the substrate W and the edge ofthe recess 20 by means of an opening 31 that extends around the recess20. The duct 32 is, in a similar manner to that discussed above,connected to an under-pressure source or channel 34 to an under-pressuresource in order to extract fluid from the gap. In the localized area,corresponding to the position of a positioning feature 25 on thesubstrate W when appropriately placed on the substrate table, theopening into the duct 32 is enlarged, providing an enlarged opening 75.

FIG. 14 depicts a cross section of the fluid extraction system throughthe enlarged opening 75 connecting to the duct 32 and FIG. 15 depicts afront-on view of the enlarged opening 75 looking from the substrate W.As shown, the width of the enlarged opening 75 at the localized sectionof the gap between the substrate W and the edge of the recess 20corresponding to the location of the positioning feature 25 is greaterthan the width of the opening 31 along the remainder of the opening.Accordingly, the resistance to fluid flow is lower at this point,resulting in a greater fluid flow from the gap between the edge of thesubstrate W and the edge of the recess 20 at this localized section ofthe gap.

Although, as depicted in FIG. 14, the enlarged opening 75 may have asubstantially constant cross-sectional area extending into the edge ofthe recess 20 from the point at which it opens into the gap between theedge of the substrate W and the edge of the recess 20, this need not bethe case. For example, as depicted in FIG. 16, the cross-sectional areaof the opening 76 may decrease as it passes into the edge of the recess20 from the point at which it opens into the gap 26 between the edge ofthe substrate W and the edge of the recess 20.

Likewise, although the arrangements depicted in FIGS. 14 to 16 depictthe enlarged opening at the localized area providing enlarged fluidextraction capacity as being provided by the provision of an enlargedopening within the edge of the recess 20, the enlarged opening may, asdepicted in FIG. 17 from the side and in FIG. 18 from the top, beprovided alternatively or additionally by the provision of an additionalrecess 80 within the surface of the substrate table WT. In particular,the additional recess 80 may be positioned such that it is aligned withthe positioning feature 25 of the substrate W when it is supported onthe substrate table WT and extends, for example, into the edge of therecess 20 from a location adjacent to the edge of the substrate W at thepositioning feature 25. Accordingly, in the region of the positioningfeature 25 of the substrate W, the additional recess 80 and the opening31 in the edge of the recess 20 combine together to produce an enlargedopening with the same effect as discussed above.

As depicted in FIGS. 19 and 20, the arrangement depicted in FIGS. 17 and18 may be varied such that the cross-sectional area of the enlargedopening in the edge of the recess 20 adjacent to the positioning feature25 of the substrate W decreases as it passes into the edge of the recess20 from the point at which it opens into the gap 26 between the edge ofthe substrate W and the edge of the recess 20. As depicted in FIG. 19from the side and in FIG. 20 from the top, such an arrangement may beprovided by configuring the additional recess 85 such that it becomesshallower as it passes into the edge of the recess 20.

It should be appreciated that the enlarged opening in the region of thepositioning feature 25 of the substrate W may be provided by acombination of one of the arrangements such as depicted in FIGS. 14 to16 in which the opening in the edge of the recess 20 is enlarged at alocalized section and one of the arrangements depicted in FIGS. 17 to20, in which an additional recess is provided.

As with the fluid extraction systems described above in relation toFIGS. 7 to 13, it will be appreciated that fluid extraction systemsdepicted in FIGS. 14 to 20 may be configured to provide more than onelocalized section of the gap between the edge of the substrate W and theedge of the recess 20 with increased fluid extraction capacity.

It should also be appreciated that a fluid extraction system providingtwo or more localized sections of the gap between the edge of thesubstrate W and the edge of the recess 20 with increased fluidextraction capacity need not use the same arrangement for both suchsections. Accordingly, any two or more of the above-describedarrangements to provide increased fluid extraction capacity in alocalized section of the gap may be used for different sections of thegap within one apparatus.

In one embodiment, there is provided, a substrate table for an immersionlithographic apparatus, comprising: a recess, configured to receive asubstrate of a given size, the recess having a support region forsupporting a lower surface of the substrate and an edge configured to beadjacent the edge of a substrate when it is supported by the supportregion; and a fluid extraction system, configured to extract fluid froma gap between the edge of the substrate and the edge of the recess;wherein the fluid extraction system is configured such that, in theabsence of liquid, the rate of flow of fluid extracted from a localizedsection of the gap having a given length is greater than the rate offlow of fluid extracted from another section of the gap having the samelength.

The fluid extraction system may comprise one or more first ducts,opening into the gap, configured to extract fluid from the gapsubstantially all round the substrate; and the fluid extraction systemmay comprise one or more second ducts, opening into the gap, configuredto extract fluid from the localized section of the gap.

The smallest dimension of the cross-section of the one or more firstducts may be smaller than the smallest dimension of the cross-section ofthe one or more second ducts at the point at which the first and secondducts open into the gap.

In one embodiment, there is provided a substrate table for an immersionlithographic apparatus, comprising: a recess, configured to receive asubstrate of a given size, the recess having a support region forsupporting a lower surface of the substrate and an edge configured to beadjacent the edge of a substrate when it is supported by the supportregion; and a fluid extraction system, configured to extract fluid froma gap between the edge of the substrate and the edge of the recess;wherein the fluid extraction system comprises one or more first ductsopening into the gap, configured to extract fluid from the gapsubstantially all round the substrate; the fluid extraction systemcomprising one or more second ducts, opening into the gap, configured toextract fluid from a localized section of the gap; and the smallestdimension of the cross-section of the one or more first ducts is smallerthan the smallest dimension of the cross-section of the one or moresecond ducts at the point at which the first and second ducts open intothe gap.

The one or more first ducts may open into the gap by means of one ormore openings in the edge of the recess.

The one or more first ducts may be connected for fluid flow to anopening in the edge of the recess that surrounds the recess.

The one or more second ducts may open into the gap by means of acorresponding opening formed in the surface of the substrate tablebetween the support region and the edge of the recess.

The one or more second ducts may comprise a control valve, configured tocontrol the flow of fluid through the one or more second ducts.

The one or more second ducts may comprise a bleed line that bypasses thecontrol valve.

The first and second ducts may be connected to a common under-pressuresource.

The one or more first ducts may be connected to a first under-pressuresource and the one or more second ducts may be connected to a secondunder-pressure source.

The one or more second ducts may decrease in cross-section from thepoint at which the one or more second ducts open into the gap to asecond point in the one or more second ducts, downstream from the pointat which the one or more second ducts open into the gap.

The shape of the one or more second ducts from the point at which theone or more second ducts open into the gap to the second point may be afrustro-conical shape or a trumpet shape.

The fluid extraction system may comprise at least two second ducts andthe at least two second ducts may open into the gap at respectiveopenings that are set apart from each other.

The fluid extraction system may comprise at least two second ducts andthe at least two second ducts may open into the gap at a common opening.

The substrate table may be configured to support a substrate having apositioning feature such that, when the substrate is supported by thesupport region, the positioning feature of the substrate is aligned withthe opening of the one or more second ducts into the gap between theedge of the recess and the edge of the substrate such that fluid isdrawn into the one or more second ducts directly from a space betweenthe positioning feature of the substrate and the edge of the recess.

The substrate table may be configured to support a substrate having apositioning feature that is a notch, a flat or an indentation in theedge of the substrate.

The fluid extraction system may comprise one or more ducts, opening intothe gap, configured to extract fluid from the gap substantially allround the substrate; and the one or more ducts may be connected forfluid flow to an opening in the edge of the recess that surrounds therecess; and the width of the opening may be greater at the localizedsection of the gap than the width of the opening along the remainder ofthe opening.

At the localized section, the opening through the edge of the recess maybe enlarged such that its width is greater than along the remainder ofthe opening.

At the localized section, an additional recess may be formed in thesubstrate table and may be configured to adjoin a portion of the openingin the edge of the recess such that they combine to form an opening witha greater width than the width of the opening in the recess alone.

The fluid extraction system may be configured such that there are atleast two localised sections of the gap at which the width of theopening is greater than along the rest of the gap such that the rate offlow of fluid extracted from a given length is greater than from anothersection of the gap.

In one embodiment, there is provided a substrate table for an immersionlithographic apparatus, comprising; a recess configured to receive asubstrate with an edge having a positioning feature such that a gap isformed between an edge of the substrate and an edge of the recess; andan opening configured for the passage of fluid therethrough, the openingarranged in the substrate table such that, when a substrate is receivedwithin the recess, the opening is at least partly uncovered by thesubstrate and aligned with the positioning feature of the substrate.

In one embodiment, there is provide a substrate table for an immersionlithographic apparatus, comprising: a recess configured to receive asubstrate with an edge having a positioning feature such that a gap isformed between the edge of the substrate and the edge of the recess; anopening provided in the substrate table and arranged to be located atthe gap between the edge of the substrate and the edge of the recesswhen on the substrate table, wherein a dimension of the cross-section ofthe opening is substantially the length of the positioning feature onthe substrate.

In one embodiment, there is provided a substrate table for an immersionlithographic apparatus, comprising: a recess configured to receive asubstrate; an opening in the substrate table configured such that whenthe recess receives a substrate having a positioning feature, theopening is aligned with and corresponds to the positioning feature suchthat fluid may be extracted directly through the opening from a gapbetween the substrate and the edge of the recess at the positioningfeature.

In a substrate table for an immersion lithographic apparatus asdiscussed above, the support region may comprise one or more supportpoints, configured to support a portion of the lower surface of thesubstrate, and a seal, configured to be located at the edge of asubstrate supported by the support region and configured to restrainliquid from substantially passing into under the substrate, wherein theseal may comprise a further fluid extraction system, configured toextract fluid from a space under the substrate and adjacent the edge ofthe substrate.

In one embodiment, there is provided an immersion lithographic apparatuscomprising a substrate table as discussed above.

In one embodiment, there is provided an device manufacturing method,comprising projecting a patterned beam of radiation onto a substratethrough a fluid provided in a space adjacent the substrate, wherein thesubstrate is supported in a recess on a substrate table; and extractingfluid from a gap between an edge of the recess and the edge of thesubstrate using a fluid extraction system that is configured to extractfluid from the gap, the fluid extraction system configured such that inthe absence of liquid the rate of flow of fluid extracted from alocalized section of the gap having a given length is greater than therate of flow of fluid extracted from another section of the gap havingthe same length.

In one embodiment, there is provided a device manufacturing method,comprising projecting a patterned beam of radiation onto a substratethrough a fluid provided in a space adjacent the substrate, wherein thesubstrate is supported in a recess on a substrate table; and extractingfluid from a gap between an edge of the recess and the edge of thesubstrate using a fluid extraction system that is configured to extractfluid from the gap, the fluid extraction system comprising one or morefirst ducts, opening into the gap, configured to extract fluid from thegap substantially all round the substrate, and one or more second ducts,opening into the gap, configured to extract fluid from a localizedsection of the gap, wherein the smallest dimension of the cross-sectionof one or more first ducts is smaller than the smallest dimension of thecross-section of one or more second ducts at the point at which thefirst and second ducts open into the gap.

Although specific reference may be made in this text to the use oflithographic apparatus in the manufacture of ICs, it should beunderstood that the lithographic apparatus described herein may haveother applications in manufacturing components with microscale, or evennanoscale, features, such as the manufacture of integrated opticalsystems, guidance and detection patterns for magnetic domain memories,flat-panel displays, liquid-crystal displays (LCDs), thin-film magneticheads, etc. The skilled artisan will appreciate that, in the context ofsuch alternative applications, any use of the terms “wafer” or “die”herein may be considered as synonymous with the more general terms“substrate” or “target portion”, respectively. The substrate referred toherein may be processed, before or after exposure, in for example atrack (a tool that typically applies a layer of resist to a substrateand develops the exposed resist), a metrology tool and/or an inspectiontool. Where applicable, the disclosure herein may be applied to such andother substrate processing tools. Further, the substrate may beprocessed more than once, for example in order to create a multi-layerIC, so that the term substrate used herein may also refer to a substratethat already contains multiple processed layers.

The terms “radiation” and “beam” used herein encompass all types ofelectromagnetic radiation, including ultraviolet (UV) radiation (e.g.having a wavelength of or about 365, 248, 193, 157 or 126 nm). The term“lens”, where the context allows, may refer to any one or combination ofvarious types of optical components, including refractive and reflectiveoptical components.

While specific embodiments of the invention have been described above,it will be appreciated that the invention may be practiced otherwisethan as described. For example, the embodiments of the invention maytake the form of a computer program containing one or more sequences ofmachine-readable instructions describing a method as disclosed above, ora data storage medium (e.g. semiconductor memory, magnetic or opticaldisk) having such a computer program stored therein. Further, themachine readable instruction may be embodied in two or more computerprograms. The two or more computer programs may be stored on one or moredifferent memories and/or data storage media.

The controllers described herein may each or in combination be operablewhen one or more computer programs are read by one or more computerprocessors located within at least one component of the lithographicapparatus. The controllers may each or in combination have any suitableconfiguration for receiving, processing, and sending signals. One ormore processors are configured to communicate with the at least one ofthe controllers. For example, each controller may include one or moreprocessors for executing the computer programs that includemachine-readable instructions for the methods described above. Thecontrollers may include data storage medium for storing such computerprograms, and/or hardware to receive such medium. So the controller(s)may operate according the machine readable instructions of one or morecomputer programs.

One or more embodiments of the invention may be applied to any immersionlithography apparatus, in particular, but not exclusively, those typesmentioned above and whether the immersion liquid is provided in the formof a bath, only on a localized surface area of the substrate, or isunconfined. In an unconfined arrangement, the immersion liquid may flowover the surface of the substrate and/or substrate table so thatsubstantially the entire uncovered surface of the substrate table and/orsubstrate is wetted. In such an unconfined immersion system, the liquidsupply system may not confine the immersion fluid or it may provide aproportion of immersion liquid confinement, but not substantiallycomplete confinement of the immersion liquid.

A liquid supply system as contemplated herein should be broadlyconstrued. In certain embodiments, it may be a mechanism or combinationof structures that provides a liquid to a space between the projectionsystem and the substrate and/or substrate table. It may comprise acombination of one or more structures, one or more fluid openingsincluding one or more liquid openings, one or more gas openings or oneor more openings for two phase flow. The openings may each be an inletinto the immersion space (or an outlet from a fluid handling structure)or an outlet out of the immersion space (or an inlet into the fluidhandling structure). In an embodiment, a surface of the space may be aportion of the substrate and/or substrate table, or a surface of thespace may completely cover a surface of the substrate and/or substratetable, or the space may envelop the substrate and/or substrate table.The liquid supply system may optionally further include one or moreelements to control the position, quantity, quality, shape, flow rate orany other features of the liquid.

The descriptions above are intended to be illustrative, not limiting.Thus, it will be apparent to one skilled in the art that modificationsmay be made to the invention as described without departing from thescope of the claims set out below.

1. A substrate table for an immersion lithographic apparatus,comprising: a recess, configured to receive a substrate of a given size,the recess having a support region to support a lower surface of thesubstrate and an edge configured to be adjacent the edge of a substratewhen it is supported by the support region; and a fluid extractionsystem, configured to extract fluid from a gap between the edge of thesubstrate and the edge of the recess, wherein the fluid extractionsystem is configured such that, in the absence of liquid, the rate offlow of fluid extracted from a localized section of the gap having agiven length is greater than the rate of flow of fluid extracted fromanother section of the gap having the same length.
 2. The substratetable of claim 1, wherein the fluid extraction system comprises a firstduct, opening into the gap, configured to extract fluid from the gapsubstantially all round the substrate, and a second duct, opening intothe gap, configured to extract fluid from the localized section of thegap.
 3. The substrate table of claim 2, wherein the smallest dimensionof the cross-section of the first duct is smaller than the smallestdimension of the cross-section of the second duct at the point at whichthe first and second ducts open into the gap.
 4. The substrate table ofclaim 2, wherein the first duct opens into the gap by means of anopening in the edge of the recess.
 5. The substrate table of claim 4,wherein the first duct is connected for fluid flow to an opening in theedge of the recess that surrounds the recess.
 6. The substrate table ofclaim 2, wherein the second duct opens into the gap by means of acorresponding opening formed in the surface of the substrate tablebetween the support region and the edge of the recess.
 7. The substratetable of claim 6, wherein the second duct comprises a control valve,configured to control the flow of fluid through the second duct.
 8. Thesubstrate table of claim 7, wherein the second duct comprises a bleedline that bypasses the control valve.
 9. The substrate table of claim 6,wherein the first and second ducts are connected to a commonunder-pressure source.
 10. The substrate table of claim 2, wherein thesecond duct decreases in cross-section from the point at which thesecond duct opens into the gap to a second point in the second duct,downstream from the point at which the second duct opens into the gap.11. The substrate table of claim 2, wherein the fluid extraction systemcomprises at least two second ducts and the at least two second ductsopen into the gap at respective openings that are set apart from eachother.
 12. The substrate table of claim 2, wherein the fluid extractionsystem comprises at least two second ducts and the at least two secondducts open into the gap at a common opening.
 13. The substrate table ofclaim 2, wherein the substrate table is configured to support asubstrate having a positioning feature such that, when the substrate issupported by the support region, the positioning feature of thesubstrate is aligned with the opening of the second duct into the gapbetween the edge of the recess and the edge of the substrate such thatfluid is drawn into the second duct directly from a space between thepositioning feature of the substrate and the edge of the recess.
 14. Thesubstrate table of claim 1, wherein the fluid extraction systemcomprises a duct, opening into the gap, configured to extract fluid fromthe gap substantially all round the substrate, wherein the duct isconnected for fluid flow to an opening in the edge of the recess thatsurrounds the recess and the width of the opening is greater at thelocalized section of the gap than the width of the opening along theremainder of the opening.
 15. The substrate table of claim 14, wherein,at the localized section, the opening through the edge of the recess isenlarged such that its width is greater than along the remainder of theopening.
 16. The substrate table of claim 14, wherein, at the localizedsection, an additional recess is formed in the substrate table and isconfigured to adjoin a portion of the opening in the edge of the recesssuch that they combine to form an opening with a greater width than thewidth of the opening in the recess alone.
 17. The substrate table ofclaim 14, wherein the fluid extraction system is configured such thatthere are at least two localized sections of the gap at which the widthof the opening is greater than along the rest of the gap such that therate of flow of fluid extracted from a given length is greater than fromanother section of the gap.
 18. The substrate table of claim 1, whereinthe support region comprises a support point, configured to support aportion of the lower surface of the substrate, and a seal, configured tobe located at the edge of a substrate supported by the support regionand configured to restrain liquid from substantially passing into underthe substrate, wherein the seal comprises a further fluid extractionsystem, configured to extract fluid from a space under the substrate andadjacent the edge of the substrate.
 19. A substrate table for animmersion lithographic apparatus, comprising: a recess, configured toreceive a substrate of a given size, the recess having a support regionto support a lower surface of the substrate and an edge configured to beadjacent the edge of a substrate when it is supported by the supportregion; and a fluid extraction system, configured to extract fluid froma gap between the edge of the substrate and the edge of the recess,wherein the fluid extraction system comprises a first duct, opening intothe gap, configured to extract fluid from the gap substantially allround the substrate and a second duct, opening into the gap, configuredto extract fluid from a localized section of the gap, and the smallestdimension of the cross-section of the first duct is smaller than thesmallest dimension of the cross-section of the second duct at the pointat which the first and second ducts open into the gap.
 20. A devicemanufacturing method, comprising: projecting a patterned beam ofradiation onto a substrate through a fluid provided in a space adjacentthe substrate, wherein the substrate is supported in a recess on asubstrate table; and extracting fluid from a gap between an edge of therecess and the edge of the substrate such that in the absence of liquidthe rate of flow of fluid extracted from a localized section of the gaphaving a given length is greater than the rate of flow of fluidextracted from another section of the gap having the same length.